<!DOCTYPE HTML>
<html lang="en-US">
<head>
	<meta charset="UTF-8">
	<title>js-array-concat</title>
</head>
<body>
	
</body>
</html>
<script type="text/javascript">
var a = [1,2,3];
var b = a.concat(4,[5,[6,7]]);
alert(b[b.length-1]);
</script>